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A-3 Analog Input

General Info

Below you can find general information regarding the T7's Analog input lines. For further details consult the Noise and Resolution subsection.

Table A.3-1. T7 Analog input information

  Conditions Min Typical Max Units
Typical Input Range (1) Gain=1 -10.5   10.1 Volts
Max AIN Voltage to GND (2) Valid Readings -11.5   11.5 Volts
Max AIN Voltage to GND (3) No Damage -20   20 Volts
Input Bias Current (4)     20   nA
Input Impedance (4)     1  
Max Source Impedance (4)     1  
           
Integral Linearity Error Gain=1, 10, 100     ±0.01 %FS
  Gain=1000     ±0.1 %FS
Absolute Accuracy Gain=1, 10, 100     ±0.01 %FS
  Gain=1000     ±0.1 %FS
           
Temperature Drift     15   ppm/°C
           
Channel Crosstalk (5) < 1kHz   -100   dB
  1kHz - 50kHz   20   dB/dec
           
-3dB Frequency Gain=1, 10   445   kHz
  Gain=100   337   kHz
  Gain=1000   63   kHz
           
Noise (Peak-To-Peak) See A-3-1     <1 μV
Effective Resolution (RMS) See A-3-1     22 bits
Noise-Free Resolution See A-3-1     20 bits
           
(1) Differential or single-ended     
(2) This is the maximum voltage on any AIN pin compared to ground for valid measurements on that channel. For single-ended readings on the channel itself, inputs are limited by the "Typical Input Range" above, and for differential readings consult the signal range tables in Appendix-3-2. Further, if a channel has over 13.0 volts compared to ground, readings on other channels could be affected. Because all even channels are on 1 front-end mux, and all odd channels on a 2nd front-end mux, an overvoltage (>13V) on a single channel will generally affect only even or only odd channels.     
(3) Maximum voltage, compared to ground, to avoid damage to the device. Protection level is the same whether the device is powered or not.     
(4) The key specification here is the maximum source impedance. As long as your source impedance is not over this value, there will be no substantial errors due to impedance problems. For source impedance greater than this value, more settling time might be needed.     
(5) Typical crosstalk on a grounded AIN pin, with 20Vpp sine wave on adjacent AIN pin. An adjacent AIN pin refers to multiplexer channel location not channel number, e.g. AIN0-AIN2 or AIN1-AIN3 pairs.     

2 comments

Please advise what protection exists for the analog input channels ie will they survive transients and surges over the maximum input voltage rating ?

 

The AINx lines do have overvoltage protection.  The normal input range is +/-10V, but per note #3 above the AINx lines are specified to handle up to +/-20V continuously without damage.